1. Field of the Invention
This invention relates to formulations for coloring keratin-containing fibers, more particularly human hair, which contain isatins and another compound. In one preferred embodiment, the formulations according to the invention additionally contain an ammonium or metal salt.
Keratin-containing fibers, for example hair, wool or furs, are generally colored either with substantive dyes or with oxidation dyes which are formed by oxidative coupling of one or more primary intermediates with one another or with one or more secondary intermediates. Although intensive colors with good fastness properties can be obtained with oxidation dyes, development of the color takes place under the effect of oxidizing agents, such as H.sub.2 O.sub.2 for example, which frequently results in damage to the fibers. Although substantive dyes are applied under more moderate conditions, their disadvantage is that the colors often have unsatisfactory fastness properties.
2. Discussion of Related Art
Coloring systems based on isatin or isatin derivatives offer an alternative solution. Isatin is described in DE-OS 36 35 147 A1 as a substantive dye for coloring keratin fibers either on its own or in conjunction with quinone dyes. Unfortunately, the range of variation of the color tones obtainable is limited. In most cases, a golden color is obtained.
Another isatin-containing coloring system is described in EP 359 465 A2. In this case, the color is obtained with a ketimine (Schiff's base) produced by the reaction of an isatin with an aniline derivative. The ketimine is either applied as such to keratin fibers where it develops color or, alternatively, a mixture consisting of an isatin and an aniline derivative is applied to the fibers and initially forms the ketimine in situ, after which the color develops on the fibers.
EP 497 697 A1 describes hair coloring formulations based on isatins and aminoindoles or indolines containing a primary amino group, Schiff's based being formed in a condensation reaction.
EP 0 502 783 A1 describes hair coloring formulations containing isatins and aminopyridines or isatins and aminopyrimidines containing a primary amino group.
EP 0 502 784 A1 describes hair coloring formulations containing isatins and substituted diamines or aminophenols or isatins and (bisaryl)-alkylenediamines.